Concrete and other cementitious materials contain aggregate typically stone and/or sand, and a binder, usually produced utilizing lime (calcium oxide) and other components that react with water to form a highly-networked solid when the resultant mass has cured. Calcium oxide, being highly alkaline, imparts alkalinity to the resulting water slurry. The pH of this slurry is typically over 12. As such, there is the possibility to react the residual or infiltrated water in the resultant concrete or cementitious mass (hereinafter “concrete” or “structure”), and amorphous silica in the aggregate used to make the structure. This reaction is called the alkali-silicate reaction, hereinafter sometimes referred to as “ASR”. The products of this reaction can absorb or release water, causing expansion and contraction in the concrete. If the expansion forces are locally greater than the cohesive forces in the concrete binder, then cracking results.
This cracking can be devastating to the usefulness of the structure, as in the case, for example of concrete roads and bridges. The resulting damage can drastically shorten the lifetime of the structure, causing millions of dollars in economic loss each year. Therefore, means to control, stop and/or remediate this damage have been highly sought after. Likewise, the factors that contribute to the damage have been sought after, so as not to make a bad situation worse.
Some of the major factors that contribute to ASR have been found to be the addition of water to the microscopic pores in the concrete binder, the presence of amorphous silica in the aggregate or sand added prior to mixing with water, and sources of additional alkalinity, such as alkaline cleaning solutions.
This latter factor is a source of much consternation when ASR is occurring in a concrete structure that needs periodic cleaning, such as a road, bridge or parking lot. In that situation, it is possible that the cleaning operation, while improving the appearance of the concrete, might hasten its' demise.
This is because one of the major groups of cleaning compositions, highly-utilized in the cleaning industry, especially where concrete is the substrate that is being cleaned, involve alkaline solutions. Alkalinity, often in the form of phosphates, silicates, carbonates, oxides and/or hydroxides of sodium or potassium are highly-useful to “build” up the cleaning power of cleaning compositions. They have the added advantage of being relatively inexpensive. Therefore, means of cleaning concrete utilizing alkaline cleaning compositions are very desirable if concrete that is suffering from ASR is to be cleaned.
One means that has been found to control or remediate ASR is to expose the concrete surface to lithium-containing compositions. A number of patents have been issued in the area of lithium-containing compositions and methods of utilizing them to control or remediate ASR, and these are discussed below. However, as will be shown, none of them disclose useful compositions to clean concrete structures, so compositions and/or methods of cleaning concrete structures that do not contribute to ASR are still desired.